1. Field of the Invention
This invention relates to a coupling used in orthodontic treatment. The coupling is useful for connecting force modules or other devices to other orthodontic components in the oral cavity.
2. Description of the Related Art
Orthodontic therapy is a specialized form of treatment within the field of dentistry. Orthodontic treatment involves movement of malpositioned teeth to orthodontically correct locations. Orthodontic treatment often greatly improves the aesthetic appearance of the patient's teeth and also improves the patient's occlusion, so that when the jaws are closed the upper teeth are in proper positions relative to the lower teeth.
Orthodontic therapy is often carried out by use of a system of tiny appliances, wires and other components that are commonly known collectively as “braces”. Typically, a small appliance known as a bracket is connected to each of the patient's anterior, cuspid and bicuspid teeth and an archwire placed in a slot of each bracket. The archwire forms a track to guide movement of the brackets and the associated teeth to desired positions.
End sections of orthodontic archwires are often held by appliances known as buccal tubes that are secured to the patient's molar teeth. Each buccal tube has a passage that slidingly receives the end section of the archwire. Buccal tubes may be placed on the patient's first molar teeth or the patient's second molar teeth.
In some instances, and particularly in connection with adolescent patients, the second molar tooth has often not sufficiently erupted at the beginning of orthodontic treatment to receive a buccal tube. In those instances, the practitioner may elect to install a convertible buccal tube on the patient's first molar teeth. Later, and after the second molar teeth have erupted, a buccal tube is installed on the second molar teeth and the buccal tube on the first molar teeth is converted to a bracket. Convertible buccal tubes have an enclosed passage that can be opened when desired to convert the passage into a slot that is open along one side, similar to the slots of orthodontic brackets.
In orthodontic treatment, the molar teeth often serve as convenient points of anchorage for various components because the molar teeth are relatively large and have a plurality of roots. As a consequence, many buccal tube appliances have a passage in addition to the passage for receiving the archwire slot. The additional passage (also known as an auxiliary passage) can be used for connection to other orthodontic devices as desired.
For example, the orthodontic treatment of some patients includes correction of the alignment of the upper dental arch to the lower dental arch. Certain patients have a condition referred to as a Class II malocclusion wherein the lower dental arch is located an excessive distance rearward of the upper dental arch when the jaws are closed. Other patients may have an opposite condition referred to as a Class III malocclusion wherein the lower dental arch is located forward of the upper dental arch when the jaws are closed.
In the past, correction of Class II and Class III malocclusions was often carried out by the use of a force-applying system known as headgear. The headgear includes strapping that extends around the rear of the patient's head, and the strapping is connected to a facebow having legs that are received in the passages of buccal tubes. An example of headgear is described in U.S. Pat. No. 4,368,039 to Armstrong. Optionally, each side of the strapping is connected to the facebow by a releasable coupling having a tension spring. The strapping and springs serve to apply a rearwardly-directed force to the buccal tube appliances and hence to the patient's associated jaw.
Intra-oral devices for correction of Class II and Class III malocclusions are also known. Such intra-oral devices are preferred by many patients who might otherwise be embarrassed by the appearance of headgear. Practitioners also often prefer intra-oral devices for correction of Class II and Class III malocclusions because, unlike headgear, many of those devices are fixed in place and issues of patient cooperation are avoided.
A number of intra-oral devices for correcting Class II and Class III malocclusions are known in the art. For example, U.S. Pat. Nos. 4,708,646, 5,352,116, 5,435,721 and 5,651,672 describe intra-oral devices with flexible spring members that are connected to upper and lower arches of a patient. The length of the device is selected such that the member is curved in an arc when the patient's jaws are closed. The inherent spring bias tends to urge the members toward a normally straight orientation and provide a force that pushes one dental arch forward or rearward relative to the other dental arch when the jaws are closed.
U.S. Pat. Nos. 5,645,424 and 5,678,990 describe intra-oral devices for correcting Class II and Class III malocclusions having linkage that includes pivotal connections. The devices in both of these references have an overall somewhat “Z”-shaped configuration. A device having a somewhat similar overall configuration is shown in U.S. Pat. No. 5,645,423 and includes double helical loops located on each side of a central segment. In U.S. Pat. No. 5,678,990, one of the linkages comprises a spring-loaded telescoping assembly.
Other orthodontic devices for correcting Class II and Class III malocclusions are described in U.S. Pat. Nos. 3,798,773, 4,462,800 and 4,551,095. Those devices include telescoping tube assemblies that urge the dental arches toward positions of improved alignment. Another telescoping tube assembly for repositioning the dental arches is described in U.S. Pat. No. 5,711,667. U.S. Pat. Nos. 5,562,445 and 5,964,588 also describe intra-oral devices having telescoping members.
In the past, it has been common practice to connect Class II correctors to buccal tubes using a ball pin. Examples of such connections are shown in U.S. Pat. Nos. 6,234,791, 5,964,588 and 5,651,672. As described in those references, a ball pin is threaded through an aperture located adjacent the upper end of the Class II corrector, and then directed through the passage in the buccal tube from its distal side (i.e., the side facing away from the middle of the patient's dental arch) to the mesial side (i.e., the side facing toward the middle of the patient's dental arch). The mesial end of the pin is then bent at an angle to retain the pin in place.
While ball pins provide an inexpensive and secure connection of Class II correctors to buccal tube appliances, there are inherent problems associated with the same. For example, some practitioners encounter difficulty when threading the pin through the buccal tube appliance from its distal side, particularly in instances where space in the oral cavity is restricted. Pliers are often used for placing the pin in the passage of the buccal tube appliance, but if the grip on the pin is lost, the pin may slip out of the aperture of the Class II corrector and become loose in the patient's oral cavity. Furthermore, once the pin has been correctly installed in the passage, it may be difficult to bend the end section of the pin at an angle, especially when a certain orientation is desired.
It has also been proposed in the past to use a retaining clip for connecting Class II correctors to buccal tube appliances. Such clips are somewhat similar to safety pins, in that they have a free end with a straight shank and another end with a hook that can be extended around the shank. Once the free end has been inserted into the passage of the buccal tube appliance, the clip is closed by moving the hook until the hook extends around the shank.
However, the retaining clips described above are not entirely satisfactory because they also are constructed for insertion into the passage of the buccal tube appliance from its distal side to its mesial side. Moreover, it may be difficult and somewhat time-consuming to connect the hook to the shank within the confines of the oral cavity. Clearly, there is a need for a better coupling that overcomes these difficulties.